So, to clarify, I copied a copy of Stereo Madness, and I can't upload it. I did change it quite a bit, though, so it's not completely the same as Stereo Madness. I can upload any other level, but not that one. I want to know if there is any reason that I can't upload it, like if Geometry Dash doesn't allow people to upload copied levels (though I'm pretty sure that's not the case).
Several things to check:
- You need to verify the level first by playing it yourself. I don't think you need to complete it, because I have seen levels that are incomplete (some just drop off and you have about 30 seconds of nothing; and others that are just impossible to finish due to a block being out of place, etc)
- Try upgrading to the latest version. Some changes in the versions will not allow you to upload a level if you are using an earlier version.
- Make sure you are connected to the internet (that's an obvious one).
- Make sure your profile hasn't been banned. There are several reasons why users can be banned, and this will stop you from being able to upload levels.
- File size may contribute to this issue. If a file is too large, the servers will reject it. Reduce the length of the level, or try trimming some blocks etc. to reduce the file size, and try again.